Walkway would camouflage stormwater pipes

EVERETT — The city’s latest fix for north-end sewer backups could be camouflaged inside a pedestrian walkway leading to the waterfront.

Public Works Director Dave Davis unveiled the unorthodox design Wednesday to the City Council. The bridge would complement an upcoming project to separate stormwater and sewer flows for a flood-prone section of Everett’s Northwest Neighborhood.

“We think that this is the most viable approach that will allow for the least amount of maintenance and will provide the most amount of flexibility,” Davis said.

The structure would convey stormwater — and people — from the north end of Grand Avenue Park, over the railroad tracks and W Marine View Drive. It would replace a battered pipe that now runs down the bluff and underneath the railroad tracks.

It also would be part of the solution to a messy problem that bubbles up when storm events overwhelm the city’s aging sewer system.

City leaders believe the pedestrian walkway, with elevators on both sides, would be a clever add-on to the utility bridge. It would help people reach an area of the waterfront that’s now inconvenient to access on foot. The structure would take stormwater to Port Gardner Bay, while giving foot traffic an easy pathway to the area near the Port of Everett Marina. The city could add more stormwater pipes as future sewer improvements come online.

“This is the best technology and will serve us for decades to come,” Mayor Ray Stephanson said.

Staff is likely to return to the council seeking approval for the bridge design early next year, Davis said. They’re not asking for any increase in utility rates to pay for the work.

Wednesday’s presentation gave the council its first look at long-term fixes proposed for an outdated sewer and stormwater system that was cobbled together between the late 19th century and the 1960s.

Stormwater and sewage wind up in the same pipes. Heavy rains regularly cause backups, sending untreated sewage pouring from toilets and basement drains. The sewage-fouled water also is spilled into Port Gardner instead of being routed to the city’s wastewater treatment plant.

The most recent trouble came after hard rains Aug. 29 and Sept. 6. Everett has received at least 180 related damage claims from property owners and expects to pay out about $3 million.

The bridge to the north waterfront would tie into a sewer upgrade the city already had planned long before the storms hit three months ago.

A comprehensive look and what it would take to separate sewer and stormwater in the whole city isn’t expected until next spring.

The upcoming work in the Northwest Neighborhood is known as the sewer improvement “M” project. It would be divided into two phases, plus the utility bridge.

It’s the first neighborhood sewer upgrade that would fully separate stormwater and sewer water in an area now served by a combined system, Davis said.

The sewer “M” project would upgrade service to 523 buildings, of which 376 have full or partial basements. As an interim fix, before the big capital projects are finished, city officials have recommended installing backwater valves at 150 of those buildings. The cost of installing the values is estimated at more than $500,000.

Phase one of the sewer “M” upgrade covers an area where the city received 28 claims for basement flooding related to the Aug. 29 and Sept. 6 storms. Construction would be scheduled to start next summer and finish about a year later.

The second phase, covering an area that’s generated fewer damage claims would begin in mid-2015 and finish in 2016. The bridge work would occur around the same time.

Combined, the two phases would cost an estimated $14.3 million. The bridge would cost another $6.3 million. About $2 million of the bridge cost would be for adding the pedestrian component.

The sewer “M” upgrade would only improve a small fraction of the 6,500 acres of Everett served by a combined sewer system.

“This is one-sixtieth of the area and we’re going to be spending just short of $20 million to be able to provide these types of improvements,” Davis said.

Engineers concluded that the utility bridge is the best plan for getting water to flow down the hill once the sewers there are separated, Davis said. The bridge would carry stormwater over W Marine View Drive and the railroad tracks, but would stay under Snohomish County PUD’s electricity lines.

The bridge concept is similar to a structure the state Department of Transportation built in Lowell to carry stormwater runoff from I-5. The Lowell structure sends water into ponds before it flows slowly into the nearby Snohomish River.

Unlike the WSDOT structure in Lowell, the proposed bridge in north Everett would include elevators on both sides so it would be more accessible to people with disabilities that make it difficult to use stairs.